April Kirkendoll writes in the conclusion
of her entertaining book entitled "How to Raise &
Train Your Peppermint Shrimp" to, 'tell the world what
you discover and don't skimp on the details. Our hobby may
depend on it." I sincerely believe these words, and have
tried to detail as much of my experiences attempting to raise
Peppermint shrimp, so that you might not only observe many
of the aspects of shrimp growth, but also may learn and develop
novel ways of increasing the post-larval settlement survival
rate.

For the first three years of trying to
spawn and raise Peppermint shrimp, I could never get the shrimp
larvae to survive more than a week or so before they died
en masse. Recently, however, I was able to rear them
to 5 weeks before they died by feeding copepods, in addition
to baby brine shrimp (bbs) and plankton flake food. Here's
my hobbyist's tale.

Figure 1. Breeding Adult

The Breeding Adults

Approximately three years ago, I obtained
two small Peppermint shrimp, Lysmata wurdemanni, from
a local fish store. Since then I've been able to capture roughly
half of the larvae (about 50 larvae captured) almost every
month. No special attention is given to the adult shrimp.
Generally, frozen Mysis and brine shrimp are fed to
the tank every day, as well as Tahitian Blend algae paste
(see note 1). The adult shrimp will generally eat anything
that they can catch and tear apart with their pincers. The
shrimp are full sized adults (3") ,and regularly produce
free swimming larvae every month (about 100 larvae at each
event).

Capturing Larvae

Spawning inevitably occurs late at night,
usually around midnight. If the larvae are not removed immediately
from a fully stocked reef tank, they stand very little chance
of survival because of predation by fish. In my 100 gallon
main tank, it is obvious when the larvae are present as the
presence of a swarm of shrimp larvae induces the Anthias
to go into a plankton feeding frenzy. At that point, I start
removing the larvae using a 10 ml plastic syringe with 5 inches
of airline host attached to the end. Do not attempt to use
a fine mesh net to collect the fragile larvae as the physical
contact tends to break appendages. I've observed larvae with
missing appendages circle and spin in the grow-out tank and
usually die off very soon after. Additionally, I suspect the
larvae don't feed as well as those with all appendages. The
pumps are all turned off during this process to prevent larvae
from going over the overflow, or being distributed around
the tank, making it harder to siphon them out. In dark and
still water, the larvae naturally group together on the bottom
of the tank; which makes it easier to siphon them out. If
there is light, the larvae tend to swim toward the light but
don't group together well. Even grouped together, it is quite
laborious to get them out, and I usually only manage to retrieve
about half before tiring. The fish consume the rest.

Initial Grow-Out Tank

Water from the main tank (see Table 1)
is transferred to a tiny 1/2 gallon tank containing a single
airstone that generates very fine bubbles. Fresh artificial
salt water (ASW) is not used because of very high mortality
rates (personal observation, Toonen 1999, Strathmann 1987)
possibly due to the use of Tris-EDTA or like chelator. One
workaround maybe to first run the ASW through granular activated
carbon then age under heavy aeration. If the bubbles are too
large, the larvae can be damaged from the turbulence. Again,
larvae with broken appendages appear to feed less effectively
and die sooner than larvae with all appendages. Using an extra
small tank for the initial grow-out of the larvae increases
the density of newly hatched Artemia, and provides
a higher probability that weakly swimming larvae will make
contact with the food. Brine shrimp nauplii stocking concentration
was roughly 25 per milliliter. A single 9-watt normal output
fluorescent light is used to attract both the larvae and brine
shrimp to the water surface and away from the airstone. My
next version of the rearing tank will be a tank within a tank
so I can isolate the larvae from dangerous filtration equipment.
The water temperature is kept between 74 and 78 degrees, and
no water changes are made for the two weeks of the initial
rearing period. Only RO/DI water is added, very slowly, to
keep the specific gravity roughly constant at 1.025. The chance
of changing water and inadvertently transferring larvae out
of the tank is great, and fishing larvae out of water with
a plastic 10ml suringe is not an easy task. Larval mortality
during the first two weeks is high; I estimate it to be about
50 percent. When the tank bottom begins accumulating detritus,
the larvae are transferred to the final rearing tank via a
½ inch inner diameter hose to reduce the chance of
larvae becoming trapped in the bottom debris (Castro, 1983).

Table 1: Main
Tank Water Chemistry

Temp

79.5 - 82.5 deg F

pH

7.95 to 8.22

ORP

278 - 300

Specific Gravity

1.025

NH3

Not detectable

NO2

Not detectable

NO3

1.0 ppm

Alk

8.0kH/2.86 meq

Ca

450 ppm

Mg

1250 ppm

PO4

<0.05 ppm

BART-HAB

12 hour incubation

Larval Rearing Tank

A 10 gallon rearing tank is set up in parallel
to the initial grow-out tank using water from the main tank,
and any copepods are allowed to grow under 40 watts of normal
output fluorescent light. Additionally, copepod growth is
encouraged by additions of cryopreserved algae (see note 1).
After two weeks, the surviving larvae from the initial grow-out
tank are transferred via hose to the rearing tank. Freshly
hatched Artemia nauplii are added every other day at
a density of about one fifth of what it was in the mini-tank
(about 5 per milliliter). However, since the larvae are bigger
and are better swimmers with more appendages, finely smashed
dried plankton flake is added to the tank as well (Kirkendoll
2001). It is believed that 2-4 week old larvae eat bbs, phytoplankton
(Toonen, personal communication 2002; Jaime 2000; Ronquillo
1997), flake food (Kirkendoll 2001) and baby copepods (personal
observation; Shishehchian 1999). I've observed 5 week old
larvae catch a copepod and eat it, look quite fat afterwards
and pigmentation increases afterwards. (See photos 1 &
2 of 4-week old larvae ). Toonen believes (personal communication,
2002) shrimp larvae consume some amount of phytoplankton as
part of their diet since shrimp larvae have phyllopodous legs
that are typically an adaptation for filter-feeding in marine
invertebrate larvae. Toonen has also found Lysmata
larvae guts loaded with phytoplankton (Tahitian Isochrysis
) fed hours before. Toonen (pers. comm., 2002) believes only
live phytoplankton (e.g. DT's Phytoplankton) should be used
since the chemical used to preserve algae paste contributes
to sticky surface films and hence a greater chance of trapping
larvae.

Figure 2: 4 week old [side
view]

Figure 3: 4 week old [top view]

Copepods

I do not know what species of copepod
grow abundantly on the glass surfaces of the 10 gallon tank,
but I believe them to be harpacticoids (Shimek, personal communication,
2002). The young white copepods (1-2 mm) often dart out into
the water column to move from place to place or so make small
forays into the water to catch food and are occasionally caught
by larvae. The copepods are clearly benthic, spending most
of their time in the bottom debris or on the tank sides. The
copepods in my tank under 40x magnification have long twin
first antennae in the front and very long twin 'tails' in
the end (see Figure 4 for an approximate sketch). The females
carry sacks of eggs in the tails. These copepods appeared
to reproduce rapidly under 40 watts of normal output fluorescent
light, daily algae paste and brine shrimp nauplii additions.

Figure 4.

The adults (5 mm) do not exhibit
darting behavior and spend most of their time near the bottom.
My theory is that the shrimp larvae are able to catch the
free-swimming copepod juveniles as they dart out, even though
the copepods are much faster swimmers. Occasionally, I would
see a shrimp larvae jerk in response to being hit by a young
copepod 'missile,' and then retreat. The shrimp larvae intestines
contained colored contents (probably flake food), as well
as white/gray matter (probably bbs and, I believe, the small
copepods). Copepods are believed to be a good larvae food
source because copepods are high in EPA/DHA (Toonen, personal
communication, 2002) and waxy esters and marine oils (Hoff
1999). Strathmann (1987) reports some epibenthic harpacticoid
species are heavily preyed upon by juvenile salmon.

Larval Settlement

According to Riley (1994), Lysmata
settlement can occur anywhere between 40 and 65 days, and
it is not clear exactly what settlement cue triggers the larvae
to become post larvae shrimp. The earliest settlement of 42
days by L. amboinensis was observed at the Waikiki
Aquarium in a special 1000 gallon flow-through system using
natural seawater, and the larvae were fed heavily on Tetraselmis
and rotifers, switching to enriched Artemia at a later
time (Toonen, personal communication with Waikiki Aquarium
staff, 2002).

Conclusion

I was not able to get larvae past
5 weeks even though the larvae were large (1cm), colorful,
and were freely using their pleiopods to swim towards food.
I believe my high mortality rate at week 2 then again at week
5 were do to the following four issues that will be the focus
of follow-up experiments:

Entrapment of larvae on bottom debris and on sticky slime/film
on the tank surface do to use of preserved algae paste.
I've already redesigned the larvae growout tank so that
larvae are contained in a inside tank with mesh bottom and
side to encourage detritus to fall into the outside water
column and processed by mechanical and biological filters
(Strathmann 1987)

Poor water quality. I did not actively measure nitrogenous
waste, but there was tremendous algae growth on the bottom
and sides of tank. I plan to reduce the amount of light
in the growout tank from 40 to 20 watts of fluorescent light,
replace 50 percent of the tank water per day from my main
tank and routinely test for ammonium and nitrite ions.

Poor food quality. The majority of brine shrimp napulii
were not the characteristic orange color they should be
for newly hatched San Francisco Bay Brand brine shrimp but
were pale brown. I don't have the means to measure fatty
acid content of the brine shrimp but they didn't look as
good as I've seen them. To ensure the nauplii are as nutritious
as possible, I've purchased a new lot of premium grade San
Francisco Bay Brand from Brine
Shrimp Direct and will feed a mixture of nauplii and
brine shrimp gut loaded with algae paste and SELCO.

Physical damage/stress due to collection and aeration
of water. Even using a large 10 ml syringe and gentle aeration
I personally observed several larvae with missing appendages.
There may be other stress indicators but physical damage
is the most obvious. I'll probably try using the overflow
and capture method mentioned by Strathmann (1987) where
Zoeae are isolated in a baffle system. The missing appendages
weren't simply the result of a molt, but a single missing
appendage that caused the larvae to spin uncontrollably.

The author wishes to thank Dr. Ron
Shimek, Eric Borneman and the Saltwater Enthusiasts Association
of the Bay Area (SEABay) board members for reading and criticizing
the paper. Special thanks to Rob Toonen, larval biologist,
for advice and references on phytoplankton, marine invertebrate
larvae diets and settlement.